Exhaust gas treatment systems for internal combustion engines, including but not limited to diesel engines, may include an oxidation catalyst, often referred to as a diesel oxidation catalyst when coupled to a diesel engine, for treating a flow of exhaust gas from the engine. The oxidation catalyst is a flow through device that consists of a canister containing a substrate or honeycomb-like structure. The substrate has a large surface area that is coated with an active catalyst layer. As the exhaust gases traverse the active catalyst layer, carbon monoxide, gaseous hydrocarbons and liquid hydrocarbon particles, i.e., unburned fuel and/or oil, are oxidized, thereby reducing harmful emissions.
However, in order for the active catalyst layer to oxidize the carbon monoxide, gaseous hydrocarbons and liquid hydrocarbon particles, the active catalyst layer must be at or above a light-off temperature. Often, once the active catalyst layer reaches the light-off temperature, additional hydrocarbons are injected into the flow of exhaust gas through either late post fuel injection or a hydrocarbon injector. The additional hydrocarbons injected into the flow of exhaust gas may be ignited to further heat the flow of exhaust gas. The injection rate of the hydrocarbons may be increased at an acceleration rate, i.e., ramped up over time. The hydrocarbon injection rate is ramped up, i.e., accelerated, as quickly as the system allows to minimize regeneration time.
The performance of the oxidation catalyst degrades over time with usage of the vehicle due to the loss of the active catalyst material and/or sintering caused by high exhaust gas temperatures. This degradation may cause an increase in the light-off temperature, which may lead to quenching of the oxidation catalyst. Quenching of the oxidation catalyst is defined as the cessation of hydrocarbon oxidation that occurs when the temperature of the active catalyst layer decreases below the light-off temperature. Quenching of the oxidation catalyst may cause excessive hydrocarbons to slip past the oxidation catalyst, thereby reducing the performance of the exhaust gas treatment system, or may result in collection of hydrocarbons on the substrate of the oxidation catalyst, which may lead to excessive temperatures once the light-off temperature is reached and the collected hydrocarbons begin to oxidize.